Mkoji G M, Hofkin B V, Kuris A M, Stewart-Oaten A, Mungai B N, Kihara J H, Mungai F, Yundu J, Mbui J, Rashid J R, Kariuki C H, Ouma J H, Koech D K, Loker E S
Biomedical Sciences Research Center, Kenya Medical Research Institute, Nairobi.
Am J Trop Med Hyg. 1999 Nov;61(5):751-9. doi: 10.4269/ajtmh.1999.61.751.
The Louisiana red swamp crayfish, Procambarus clarkii, which was introduced into east Africa in the 1950s or 1960s, has since widely dispersed. Previous work by our group has shown that P. clarkii can reduce populations of the molluscan intermediate hosts of human schistosomes through predatory and competitive interactions. Here, we investigate whether crayfish can reduce populations of Bulinus africanus and consequently, Schistosoma haematobium prevalence in school children. Children from 6 primary schools in the Machakos and Kitui Districts of Kenya were selected for study. Schools were divided into 3 experimental-control pairs. At experimental schools, crayfish were introduced into nearby aquatic habitats harboring Bulinus africanus snails and serving as S. haematobium transmission sites. Snail habitats near control schools did not receive crayfish. Six months after crayfish introduction, all infected children were treated with praziquantel. Children were then monitored quarterly for 2 years, at which time infection and reinfection rates were compared statistically between the paired schools. In one such pair, crayfish failed to establish, resulting in neither snail control nor a reduction in transmission. At the second pair of schools, the numbers of snails were decreased by the presence of crayfish, but a clear difference in infection rates in children could not be detected, primarily because drought conditions kept overall transmission rates low. At the third school pair, crayfish established well in experimental habitats, snail numbers decreased precipitously, and children at the experimental school were significantly less likely to acquire S. haematobium infections than children at the control school. Our results indicate that under certain environmental circumstances, P. clarkii exerts a significant impact on the transmission of human schistosomiasis in Kenya. Important questions remain regarding the impact of P. clarkii on Kenyan freshwater ecosystems, not the least of which is its potential to significantly influence the epidemiology of schistosomiasis in east Africa.
路易斯安那州红沼泽螯虾（克氏原螯虾）于20世纪50年代或60年代被引入东非，此后广泛扩散。我们团队之前的研究表明，克氏原螯虾可以通过捕食和竞争相互作用减少人类血吸虫病的软体动物中间宿主数量。在此，我们研究螯虾是否能减少非洲泡螺数量，进而降低小学生的埃及血吸虫感染率。从肯尼亚马查科斯和基图伊地区的6所小学选取儿童进行研究。学校被分为3组实验 - 对照对。在实验学校，将螯虾引入附近有非洲泡螺且作为埃及血吸虫传播场所的水生栖息地。对照学校附近的螺类栖息地未引入螯虾。引入螯虾6个月后，所有感染儿童均接受吡喹酮治疗。然后对儿童进行为期2年的季度监测，届时对配对学校之间的感染和再感染率进行统计学比较。在其中一组配对中，螯虾未能定居，既未控制螺类数量，也未减少传播。在第二组学校中，螯虾的存在使螺类数量减少，但未检测到儿童感染率有明显差异，主要是因为干旱条件使总体传播率较低。在第三组学校中，螯虾在实验栖息地良好定居，螺类数量急剧减少，实验学校的儿童感染埃及血吸虫的可能性明显低于对照学校的儿童。我们的结果表明，在某些环境条件下，克氏原螯虾对肯尼亚人类血吸虫病的传播有显著影响。关于克氏原螯虾对肯尼亚淡水生态系统的影响，仍存在重要问题，其中最重要的是其对东非血吸虫病流行病学产生重大影响的可能性。
